Old tires bounce back as new rubber products

ED STARK thanks his wife in part for an idea that promises to turn the world's mountains of discarded auto tires into a host of valuable new products - from gaskets to storage bins, railroad crossing pads, even to new tires again. Already the system has begun eating away at Minnesota's waste-tire pile. It will soon begin doing the same thing in Massachusetts and Michigan.

The beauty of the system, called Tirecycle, is that it makes no environmental compromises. It uses no water, so it has no contaminated effluent to dispose of. It has no smoking stack, be-cause combustion is no part of the process. It uses electrical power only.

Almost a decade ago Carol Stark pointed out to her husband that the basement was cluttered and that most of the clutter was his. The polymer chemist began sorting through some old research papers and came across one on an experiment that hadn't paid off. It involved using a polymer his Minneapolis-based company - Rubber Research Elastomerics - developed to make a particleboard that was both flexible and waterproof.

The concept worked but no one in industry saw much merit to the product, so research ended. It was another of the roughly 350 ideas chemists routinely try out for every one that succeeds commercially. Suddenly Stark realized that the polymer involved in the experiment had properties that might help in the latest project he was tackling: the need to revitalize cured rubber so it could be made into something else.

The idea worked. By coating the ground particles with the polymer, the ``dead'' rubber was rejuvenated, making it possible for the ground particles to bond together again as effectively as uncured, virgin material. In effect the little particles were made to behave like tiny segments of Velcro that locked together tightly after being molded or extruded.

At the time, Stark had in mind the waste, often as high as 20 percent, that is a part of all rubber manufacturing. The idea of tackling discarded tires hadn't occurred to him. That came when he began looking for crumb rubber to experiment with and someone provided finely ground tire waste, which is sometimes used as an additive to asphalt. It worked well. As his son, John Stark III, chief operating officer of the company, puts it: ``We suddenly realized that we had a source of raw material that would virtually never run out.''

America runs on wheels, rubber wheels for the most part, and the nation's truck and car drivers dispose of more than 240 million tires each year. That's roughly one tire for each man, woman, and child in the country. In addition, some 2 billion tires litter the countryside in official waste-tire dumps, or unofficially in rivers and streams. Still others have gone into landfills.

But buried tires have the unhappy knack of working their way back to the surface again, and from time to time stored tires catch afire. Once such a pile of tires starts burning, the fire can only be contained, not extinguished. In 1983 the 7 million tire dump in Winchester, Va., caught fire on Halloween night. It finally burned itself out the following June.

Recycling has proved very challenging in the past. Adding ground rubber to asphalt is cost effective, but only a tiny fraction of waste rubber can be used up in this way. Burning tires as a fuel source carries with it the environmental concerns associated with all incineration. Pyrolysis, which extracts oil from tires, is effective in the laboratory but has never proved economic in the real world.

The Tirecycle system converts tire waste into a raw material that is half the cost of virgin rubber and is cheaper than plastic. It combines readily with virgin rubber and all plastics.

The Tirecycle plant here can process 3 million tires a year. It is expected to consume all new tire waste generated within the state - and slowly deplete Minnesota's stockpile of tires. Only then will the state, which financed the Babbitt plant, allow the import of waste tires from outside.

In 1984 Minnesota passed legislation strictly controlling the disposal of waste tires. Early recommendations were that the only feasible solution was converting the tires into fuel. When the Tirecyle solution was presented, the state liked what it saw, for several reasons.

Ed Welsch of Minnesota's Waste Management Board, which is charged with overseeing all tire disposal within the state, explains: ``They [Tirecycle] had the documentation to support all their claims.'' The state also appreciated that ``a raw material was being produced without any trade-offs in pollution. It's a totally clean process.''

The chemistry involved had proved itself. ``It wasn't just theory,'' Mr. Welsch says. Products made from the recycled rubber were there to be seen and handled. They had stood the test of time. Truck tires, retreaded with formulas ranging from 40 to 50 percent recycled rubber, averaged 50,000 miles in real-world, on-road testing.

Finally, the technology to grind up tire waste and to separate the metal and fibers from the rubber had been in place for decades. So Minnesota financed the Tirecycle plant in Babbitt, about 230 miles north of Minneapolis.

The state chose the site in an effort to boost employment in the economically strapped region. Ideally such a plant would be closer to more heavily populated regions where more tire waste accumulates. But even at this remote site, the economic viability of the system was evident within the first year of operation. Before the state clamped a Minnesota-tires-only restriction on the plant, waste dealers brought tires from as far away as Chicago (750 miles distant). ``If Tirecycle can work here,'' John Stark avers, ``it'll work anywhere.''

The states of Massachusetts and Michigan share that confidence. James Hoyte, secretary of the Office of Environmental Affairs in Massachusetts, says: ``After having looked at a number of tire disposal methods, including burning, shredding, and tire-derived fuel, we believe that Rubber Research's Tirecycle process is the best option for the Commonwealth.''